Method and device for producing a tubular article having a circumferential accumulation of material

Abstract: In a method for producing a tubular article (1) having a circumferential accumulation of material, the tubular article (1) is formed with first engagement means (6) for engaging corresponding second engagement means on a separate ring (5), which is pushed over the article (1) to the position where the accumulation of material is to be provided until the engagement means are brought into permanent engagement with each other, so that axial displacement of the ring (5) is prevented and the accumulation of material is formed. The method is especially well suited for producing such bottles as are to have a circumferential thick flange at the opening (4). A device for carrying out the method comprises a tool having means (7) for expanding the ring (5) and applying it on the article (1) in the position where the accumulation of material is to be provided, thus establishing the engagement between the cooperating engagement means.

Description: The present invention relates to a method and a device for producing a tubular article having a circumferential accumulation of material. Relevant background art on which the preambles to appended claims 1 and 2 are based, is disclosed in EP-A-0 549 987. In the production of tubular plastic articles having a relatively thin wall, it is often desired to arrange a circumferential accumulation of material on some part of the article. One example of this is an injection liquid container or vial which at its opening should have a substantial accumulation of material to form a circumferential flange on which a closure means in the form of a cap or a cork is to be applied. In many cases, the accumulation of material should be 3-10 times the wall thickness of the container. Plastic articles of this type are generally produced by conventional techniques, such as extrusion blowing, starting from an extruded hose which is finally shaped in a special tool. Providing, in connection with such shaping, accumulations of material of the aforementioned type is very difficult, since the wall thickness of the extruded hose must be varied. The hose should be thick where a large wall thickness, i.e. accumulation of material, is desired, but thin where a small wall thickness is desired. There are certainly various techniques for automatic hose control during operation, but these techniques are both complex and costly because the hose sections having a large wall thickness must be cooled before the final shaping of the article. According to an alternative method, which has been put into practice, a thin-walled blank is produced in a first step, and is moved on to another moulding machine where, in a second step, an accumulation of material is applied by injection-moulding in the desired place on the thin-walled blank. This method has been applied e.g. in the making of infusion liquid containers whose filling neck should have a connecting portion with accumulated material, into which a rubber stopper is pressed and which is sealed by an aluminium cap. This method is however slow and costly, in that it comprises several operations which must be performed in different machines. Besides, narrow tolerance requirements are placed on the extruded blank, which are difficult to comply with and which sometimes lead to considerable scrapping. There is thus a need for a simpler and cheaper method for providing accumulation of material on such thin-walled, tubular plastic articles. One object of the present invention therefore is, while overcoming the above-mentioned drawbacks, to provide a new method by means of which a tubular, thin-walled article is provided with a circumferential accumulation of material in a less complicated and less expensive way than has hitherto been possible with existing methods. Another object of the invention is to provide a device for carrying out the method. A specific object is to apply the accumulation of material purely mechanically on a preformed, tubular blank having a thin wall. These and other objects, which will appear from the following description, have now been achieved by means of methods comprising the steps recited in appended claim 1 and 2. The objects of the invention are also achieved by means of a device as recited in appended claim 5. Preferred variants and embodiments of the invention are recited in the appended subclaims. According to the invention, the tubular article is thus formed with first engagement means for engaging corresponding second engagement means on a separate ring, which is passed over or into the article to the position where the accumulation of material is to be provided until the engagement means are brought into permanent engagement with each other, so that axial displacement of the ring is prevented and the accumulation of material is formed. The invention will be described in more detail hereinbelow with reference to the accompanying drawings which schematically show some embodiments of the invention. Fig. 1 is a part-sectional view showing a container having an accumulation of material provided in accordance with the invention. Fig. 2 shows equipment used for providing the accumulation of material on the container of Fig. 1. Figs 3-5 are part-sectional views showing different variants of the engagement between an external ring and a neck portion of a container, on which the accumulation of material is to be provided. Fig. 6, which is similar to Fig. 1, shows a container where the accumulation of material is formed with an external thread. Fig. 7 is a cross-section taken along line VII-VII in Fig. 6. Figs 8-9 are part-sectional views showing two variants of the engagement between an internal ring and a neck portion of a container, on which the accumulation of material is to be provided. Fig. 10 is a part-sectional view showing a bellows which is provided at each end with an accumulation of material according to the invention. In Fig. 1, there is shown a tubular article produced in accordance with a first aspect of the invention and being in the form of an injection liquid container or vial of plastics, generally designated 1. The container 1 has a cylindrical body 2, a tubular neck portion 3 and an opening 4. A separate ring 5, which will be described in more detail hereinbelow, is applied on the neck portion 3. A circumferential accumulation of material is formed at the opening 4 by the ring 5 and the section of the wall of the neck portion 3 where the ring 5 is applied. For example, the accumulation of material should form a strong stiffening flange for receiving a snap-action cover or the like. The method and the device according to the first aspect of the invention appear from Fig. 2. The thin-walled container 1 is manufactured in known manner by some conventional method, e.g. extrusion blowing, a circumferential groove 6 being formed in the neck portion 3. At the opening 4, the neck portion 3 has the diameter D 1 . The ring 5, here being of an elastic plastics material, is placed on a schematically illustrated, tubular expanding mandrel 7, which is first expanded radially in the direction of the arrows A and then moved axially downwards in the direction of the arrow B. Before this axial displacement, the expanding mandrel 7 has been expanded to such an extent that its internal diameter D 2 exceeds the external diameter D 1 of the neck portion 3. When the expanding mandrel 7 has been moved so far downwards that the ring 5 is on a level with the groove 6 of the neck portion 3, the expanding mandrel 7 is compressed and withdrawn upwards, the ring 5, optionally with the aid of a retaining means (not shown), being brought into permanent engagement with the groove 6 (see Fig. 1). The inner portion 8 of the ring 5 (Fig. 1) thus forms first engagement means for cooperatively engaging corresponding second engagement means in the form of the groove 6 in the neck portion 3. These cooperating engagement means 6, 8 are thus brought into permanent engagement with each other, so that axial displacement of the ring 5 is prevented and so that an accumulation of material is formed by the ring 5 and the adjoining wall section of the neck portion 3 at the groove 6. Thus, the container 1 is produced in known manner, but is formed with the groove 6, in which the ring 5 is subsequently brought into engagement by a simple operation and by simple equipment. Figs 3-5 show different alternatives of the engagement between the ring and the groove in the neck portion 3. In Fig. 3, the external ring 5a has square cross-section, like the groove 6a in the neck portion 3. Other polygonal cross-sections are of course conceivable. In the variant shown in Fig. 4, the ring 5b has on its inside a circumferential bead 9 for engaging a mating external groove 6b in the neck portion 3. According to the variant in Fig. 5, the ring 5c has a circumferential groove 10 for engaging a mating external bead 6c in the neck portion 3. In Fig. 6, there is shown a container 11 which is similar to the container in Fig. 1 with the exception of the ring 5d having an external engagement means, here shown as a screw fitting or thread 12, for a closure device, for instance a cap, a cover or the like (not shown). The engagement means may also be of the snap-action type. As shown in Fig. 7, the container 11 has in its neck portion external engagement means, here in the form of axial ridges 13, to prevent rotation of the ring 5d applied on the neck portion. The ridges 13 engage mating recesses in the ring 5d. As further seen in Fig. 7, the neck portion has a wall thickness which is considerably smaller than the thickness of the ring 5d in the central plane thereof. The thickness ratio preferably is from 1:10 up to 1:3. Figs 8 and 9 show a second aspect of the invention in which the ring 5e and 5f, respectively is applied on the inside of the neck portion 3, here being in the form of a collar. The accumulation of material is provided as before by means of the ring 5e or 5f and the adjoining wall section of the neck portion 3. The outside of the ring 5e or 5f forms engagement means for engaging corresponding engagement means in the form of a circumferential groove in the neck portion 3 in a manner similar to that described above. The rings 5e and 5f are brought into their positions of engagement either by compressing the ring or by slightly expanding the neck portion in the area of the opening. If required, the rings 5e and 5f can be provided with internal engagement means, e.g. a thread for a screw plug or similar closure device (not shown). Moreover, cooperating engagement means (not shown) can be arranged on the outside of the ring 5e or 5f and the inside of the neck portion 3 to prevent rotation of the ring. Generally speaking, the desired locking engagement for providing the accumulation of material can be brought about, for example in the following way. In the case of an external ring, this is expanded while the neck portion remains undeformed (Fig. 2). Alternatively, the neck portion is compressed while the ring is not deformed (not shown). In the case of an internal ring, this is compressed while the neck portion is not deformed (not shown). Alternatively, the neck portion is expanded while the ring is not deformed (Figs 8 and 9). It is understood that the above-mentioned methods of deformation can of course be combined, e.g. by compressing the ring when it is to be disposed internally while at the same time expanding the neck portion. In those cases where the ring is to be expanded or compressed, it consists of an elastic plastics material, e.g. polyolefin. When the ring is not to be deformed, it preferably consists of a relatively hard plastics material, e.g. polystyrene. The ring is suitably injection-moulded in a multiple tool. The invention is generally applicable and highly versatile. Fig. 10 shows an article in the form of a thin-walled bellows 18 which is provided at each end with an accumulation of material 19 and 20 according to the invention. In this case, the accumulations of material 19, 20 form connections for pipe conduits, hoses or the like (not shown). It is understood that the article to which the invention is applied may consist of different materials. The container shown in Fig. 2 might for example have a body of metal and a neck portion of plastics and vice versa. Finally, it should be pointed out that the invention is by no means restricted to the embodiments described in the foregoing, but several modifications thereof are conceivable within the scope of the inventive concept as defined in the appended claims. As mentioned above, the invention can be used in many different instances where it is desirable to provide an accumulation of material on a tubular plastic article. The purpose of the accumulation of material itself, whose thickness preferably is about 3-10 times the wall thickness of the article, is not decisive of the invention.

Claims: A method for producing a tubular article (1) having a circumferential accumulation of material, in relation to which the article has a thin wall, comprising the steps: that the tubular article (1) is formed with engagement means (6) for cooperatively engaging corresponding engagement means (8) formed on a separate, annular element (5; 5a; 5b; 5c; 5d); that the annular element is passed over the tubular article (1) to the position where the accumulation of material is to be provided; and that the cooperating engagement means (6, 8) in said position are brought into permanent engagement with each other so as to prevent axial displacement of the annular element and so as to provide the accumulation of material from the annular element applied to the tubular article (1) and from the adjoining wall of the tubular article; characterised in that the annular element (5; 5a; 5b; 5c; 5d) is first expanded and then passed over the tubular article (1); or that the tubular article is compressed before passing the annular element over it. A method for producing a tubular article (1) having a circumferential accumulation of material, in relation to which the article has a thin wall, in which method the tubular article (1) is formed with engagement means for cooperatively engaging corresponding engagement means formed on a separate, annular element (5e; 5f), characterised in that the annular element (5e; 5f) is passed into the tubular article (1) to the position where the accumulation of material is to be provided; and that the cooperating engagement means in said position are brought into permanent engagement with each other so as to prevent axial displacement of the annular element and so as to provide the accumulation of material from the annular element applied to the tubular article (1) and from the adjoining wall of the tubular article; wherein the annular element (5e; 5f) is first compressed and then inserted in the tubular article (1); or wherein the tubular article is expanded before inserting the annular element therein. A method as claimed in claim 1, wherein the annular element (5; 5a; 5b; 5c; 5d) is applied on the outside of a neck portion (3) of the article (1), which preferably is a container or a bottle. A method as claimed in claim 2, wherein the annular element (5e; 5f) is applied on the inside of a neck portion (3) of the article (1), which preferably is a container or a bottle. A device for carrying out the method as claimed in any one of claim 1-4, characterised by a tool for applying the annular element (5; 5a; 5b; 5c; 5d; 5e; 5f) outside or inside the tubular article (1), said tool having means (7) for expanding either the annular element or the tubular article, or for compressing either the annular element or the tubular article, and for applying the annular element on the article in the position where the accumulation of material is to be provided, thus establishing the engagement between the two cooperating engagement means. A device as claimed in claim 5, wherein said means of the tool is an expanding mandrel (7).

Inventors: PEDERSEN CARSTEN, PEDERSEN, CARSTEN
Applicants: PLM AB
Application year: 1994
Main classification: B65D1
IPC codes: B65D1